How many fixtures can it run at once?

Up to two or three, such as a shower plus a sink or laundry. Running more at the same time will split the flow.

Does it work with propane?

No. It is built for natural gas only and is rated at 98,500 BTU.

Can I install it myself?

Owners report easy swaps from old tank heaters, but gas line work should be done by a licensed installer. The manual's section on the gas inlet rubber rings is unclear, so check that connection carefully.

Where can it be mounted?

Indoors, in a residential setting. It is about 21 inches high, 13 wide and 7 deep, so it fits small closets and utility rooms.

How steady is the water temperature?

The control chip adjusts heating power continuously to hold output within about ±1°F, and owners report no sudden swings.

What comes in the box?

The heater, installation kits and a user manual.

What do buyers say about the 4.05 GPM Residential Natural Gas Tankless Water Heater?

Rated 4.8 out of 5 from 45 ratings. Buyers like: Easy, straightforward installation, often a DIY swap from an old tank heater; Instant, endless hot water that keeps up with multiple fixtures; Stable temperature with no sudden hot or cold swings. Common complaints: Instructions are roundabout and unclear about the rubber rings on the gas inlet; One unit arrived with the output temperature sensor not connected.

4.05 GPM Residential Natural Gas Price History: Lowest $369.99

Q: Where is the 4.05 GPM Residential Natural Gas Tankless Water Heater cheapest?

At ThermoMate, for $369.99, as of our latest check.

What reviewers say

4.8 / 545 ratings

Owners rate it highly and most describe an easy swap from an old tank heater. They praise endless hot water, stable temperatures and the small size, and several noticed lower gas bills. Complaints center on confusing instructions and one unit that arrived with a sensor unplugged.

What people mention

InstallationPraisedOwners say the swap from an old tank heater is straightforward and often a DIY job.
Hot water supplyPraisedBuyers report instant, endless hot water that keeps up with multiple fixtures.
Temperature stabilityPraisedReviewers say output stays steady with no sudden hot or cold swings.
SizePraisedOwners like the compact body, which frees space in small closets and utility rooms.
InstructionsCriticisedThe manual is described as roundabout and unclear about the rubber rings on the gas inlet.
Build qualityMixedOne buyer received a unit with the output temperature sensor not connected.

From ThermoMate

Delivers up to 4.05 GPM of instant hot water, enough for 2-3 fixtures at once
98,500 BTU natural gas tankless design with no warm-up wait
Multiple safety protections: boil-dry, overheat, water leak, anti-freeze, flame failure and high water pressure
Oxygen-free copper heat exchanger for heat transfer and corrosion resistance
Built-in chip adjusts heating power 20,000 times per second, holding temperature within ±1°F
Compact 21" high x 13" wide x 7" deep, saving over 200% of space versus tank heaters

Materials: High-quality oxygen-free copper heat exchanger
Guarantee: Comprehensive Warranty System; optional 1- or 2-year extended protection available after the standard manufacturer warranty ends
Returns: 30-Day Return (New & Unused); buyer's remorse returns are refunded at 80% of the total, defective returns get a full refund
Shipping: Free shipping to U.S. Mainland addresses only; Alaska, Hawaii, Virgin Islands, Puerto Rico, Guam and Canada are not free and freight is paid by the buyer
In the box: ThermoMate 98,500 BTU Natural Gas Tankless Water Heater, Installation Kits, User Manual

About the 4.05 GPM Residential Natural Gas Tankless Water Heater

This ThermoMate tankless water heater runs on natural gas and heats water on demand, so there is no tank to fill and no warm-up wait. It is rated at 98,500 BTU and delivers up to 4.05 gallons per minute, enough to serve 2-3 fixtures at the same time, such as showers, a dishwasher or laundry.

The heat exchanger is made of oxygen-free copper, which provides heat transfer and corrosion resistance. A water flow sensor and a built-in chip adjust the heating power 20,000 times per second. This holds the water temperature within ±1°F.

The unit is made for indoor residential use. Its compact size lets it fit in a small utility room or closet. Safety protections include boil-dry, overheat, water leak, anti-freeze, flame failure and high water pressure protection.

Heating capacity: 98,500 BTU
Flow rate: Up to 4.05 GPM
Fuel type: Natural gas
Heat exchanger: Oxygen-free copper
Temperature control: Within ±1°F fluctuation
Fixtures served: 2-3 at the same time
Installation: Indoor residential use
Dimensions: 21" high x 13" wide x 7" deep
Safety: Boil-dry, overheat, water leak, anti-freeze, flame failure and high water pressure protection
In the box: Water heater, installation kits, user manual